1. Field of the Invention
This invention relates to drive trains, and in particular to planetary gear drive trains.
2. Discussion of the Prior Art
The transmission of a three or four wheeled vehicle, such as a golf cart, typically drives the rear wheels through a differential axle. Power is input to the differential axle, typically by a shaft which is perpendicular to the axle, and gearing of the differential axle permits the wheels on opposite sides of the vehicle to turn at different speeds, which is necessary to avoid slippage between the wheel and the ground surface when turning the vehicle. The speed of the input shaft to the differential may be already reduced before it is input to the differential axle, from the speed of the motor, for example with a gear box or torque converter.
In addition to the speed reduction gearing of the motor, such a transmission requires gearing in the differential transfer case. A loss of power also results from changing the direction of rotation by 90 degrees in the differential transfer case, from the direction of the input shaft to the direction of the axle.
In addition, the wheel hubs to which the wheels are mounted, are typically journaled to the frame of the vehicle by bearings which are dedicated to that purpose. Loading the bearings of the differential is typically avoided, since the differential is usually in the center of the vehicle, and the hubs are on the sides.
Thus, a need exists for a gear reducing drive train which reduces power losses and the use of separate wheel support bearings.